The use of silicon in devices, such as thin film metal oxide field effect transistors (MOSFETs), is well known. Equally well known is the performance degradation of these devices that occurs with time. It is believed that this efficiency degradation is caused, in part, by hot carriers conducting through the channel region from source to drain. Hot carriers are electrons or holes that have high kinetic energy, which is imparted to them when voltages are applied to electrodes of the device and between the source and drain. Thus, defects within the device may arise from current flow within the device over a period of time. It is further believed that these defects reduce the mobility and lifetime of the carriers and cause degradation of the device's performance. The hot carriers impact with silicon hydrogen (Si--H) bonds at a silicon dioxide/silicon (SiO.sub.2 /Si) interface. Once the Si--H bonds are broken, the silicon dangling bonds at the interface form interfacial trap defects that reduce mobility and silicon dioxide lifetimes. To alleviate the problems caused by such dangling bonds, a hydrogen passivation process has been adopted and has become a well-known and established practice in the fabrication of such devices.
During the hydrogen passivation process, it is thought that the defects that affect the operation of semiconductor devices are removed when the hydrogen bonds with the silicon at the dangling bond sites. While the hydrogen passivation process eliminates the immediate problems associated with these dangling bonds, it does not eliminate degradation permanently because the hydrogen atoms that are added by the passivation process can be "desorbed" or removed from the previous dangling bond sites by processing conditions or by the current flow. Under such operating conditions, the hydrogen atoms, which were added by the hydrogen passivation process, can be knocked off by the processing conditions or hot carriers. This hydrogen desorption results in aging or degradation of the device's performance.
For example, during the manufacturing process, the device may be passivated with hydrogen. However, in some instances, the hydrogen may be driven off by subsequent anneal steps that may be conducted on the device. Additionally, as mentioned above, it is believed that the hot carrier flow through the device is another reason for the efficiency degradation of the above-mentioned devices. Under regular operating conditions, the hydrogen atoms, which were added by the hydrogen passivation process, are knocked off by charge carriers, and result in aging or degradation of the device's performance. The performance of the device decreases with exposure to radiation or an electric field, which limits the useful life of the device. Moreover, since the SiO.sub.2 /Si or dielectric/silicon interface is formed at a very early stage of processing, the hydrogen has to diffuse through many layers of material before reaching the SiO.sub.2 /Si interface. Thus, it is inefficient to do a hydrogen anneal.
To combat the problems associated with the use of hydrogen, the semiconductor manufacturing industry has most recently discovered that deuterium provides certain advantages over hydrogen. Because of its greater mass, deuterium atoms are not as easily removed by hot carrier flow, yet at the same time, they provide the passivation necessary to prevent or inhibit the degradation of the device. Thus, deuterium is believed to be a very good substitute for hydrogen. Unfortunately, however, it is believed that deuterium may diffuse much slower than the hydrogen, which requires a longer annealing time at added cost. In such instances, it is believed that there will still be an unacceptable loss of deuterium after the device's final anneal due to the fact that deuterium may be driven from the critical interfaces by the high temperatures associated with annealing processes.
Accordingly, what is needed in the art is a method of manufacturing a semiconductor device that provides a method of passivation such that the device does not experience levels of efficiency degradation associated with conventional processes. The present invention addresses these needs.